Magnum Opus

As Magnum Opus enters the battlefield, exile
any number of artifacts you control, put a
mastery counter on each card exiled this way.
Magnum Opus has the activated abilities of each
artifact card in exile with a mastery counter.
Creatures you control get +1/+1 for each artifact
card you own in exile with a mastery counter on
it.
Instant and sorcery spells you cast cost {1} less to
cast for each artifact card you own in exile with a
mastery counter on it.